Decomposition of Hydrogen Iodide on a Gold Surface Study
Data Collection and Analysis
In a study of the decomposition of hydrogen iodide on a gold surface at 150 °C, the following data were obtained:
| [HI], M | 0.117 | 5.85×10-2 | 2.93×10-2 | 1.47×10-2 |
|---|---|---|---|---|
| seconds | 0 | 523 | 783 | 914 |
Questions
(1) The observed half-life for this reaction when the starting concentration is 0.117 M is ..................s and when the starting concentration is 5.85×10-2 M is ..................s.
(2) The average rate of disappearance of HI from t = 0 s to t = 523 s is ....................M s-1.
(3) The average rate of disappearance of HI from t = 523 s to t = 783 s is ...................M s-1.
(4) Based on these data, the rate constant for this _______(zero/first/second) order reaction is ..................M s-1.
Answers
The observed half-life for this reaction when the starting concentration is 0.117 M is 914 s and when the starting concentration is 5.85×10-2 M is 783 s.
The average rate of disappearance of HI from t = 0 s to t = 523 s is 1.68×10-4 M s-1.
The average rate of disappearance of HI from t = 523 s to t = 783 s is 5.77×10-5 M s-1.
Explanation: The decomposition of hydrogen iodide on a gold surface at 150 °C can be represented by the equation: HI(g) → ½ H2(g) + ½ I2(g).
To determine the observed half-life for this reaction, we need to find the time it takes for the concentration of HI to decrease by half. From the given data, we can see that when the starting concentration is 0.117 M, the half-life is 914 seconds. Similarly, when the starting concentration is 5.85×10-2 M, the half-life is 783 seconds.
The average rate of disappearance of HI from t = 0 s to t = 523 s can be calculated by dividing the change in concentration by the change in time. From the given data, we can see that the concentration of HI decreases from 0.117 M to 2.93×10-2 M in 523 seconds. Therefore, the average rate of disappearance is (0.117 M - 2.93×10-2 M) / 523 s = 1.68×10-4 M s-1.
The average rate of disappearance of HI from t = 523 s to t = 783 s can be calculated in a similar manner. From the given data, we can see that the concentration of HI decreases from 2.93×10-2 M to 1.47×10-2 M in 260 seconds. Therefore, the average rate of disappearance is (2.93×10-2 M - 1.47×10-2 M) / 260 s = 5.77×10-5 M s-1.
To determine the order of the reaction, we need to analyze the relationship between the concentration of HI and the rate of disappearance. From the given data, we can see that as the concentration of HI decreases, the rate of disappearance also decreases. This suggests that the reaction is first order with respect to HI. The rate constant can be calculated using the formula: rate = k[HI]. By substituting the values from the given data, we can solve for the rate constant. However, the rate constant cannot be determined without additional information.